Cathode ray tube



June 20, 1939. J. E. BROWN ACATHODE RAY TUBE Filed Aug.- .2 1935 3 Sheets-Sheet 1 June 20, 1939. J. E. BROWN CATHODE RAY TUBE Filed Aug. 2, 1955 3 Sheets-Sheet 2 C ([656 E. Brow/20 W/mwz-M 1 M 4 7 m w a x J M Z a; 7 i 4 J lllll F 5 V g 4 flwwnmm my a m June 30, 1939. ,1. E. BROWN CATHODE an TUBE Filed Aug. 2, 1935 3 Sheets-Sheet 3 & K 5% Q 6% 6 Q atented .EuneZQ, i3

CA'EHQDE RAY Jesse E.

, Chicago, a;

Application August 2, 1935, Serial No, 343% c c. (on. 25ii-162) The present invention relates to cathode ray tubes, and is particularly concerned with improvements in the method and apparatus of cathode ray tubes for the focusing of the cathode rays.

The conventional mode of focusing cathode rays in the prior art has been by means of residual gas within the tube. Such tubes are subject to many disadvantages, and it is one of the objects of the present invention to overcome the inherent defects of the devices of the prior art mentioned. For example, in the prior devices, the residual gas molecules become ionized on being struck by high velocity electrons, and the electron beam passes through the gas and lines its path with a layer of slow-moving positive ions, the field of which efiects the desired concentration and focusing. The focusing of the beam, therefore, depends upon the amount of ionization and the quality and pressure of the gas.

Therefore, anything which affects the gas in the tube, such as temperature, progressive cleanup or pollution from occluded gas, alter the focusing. Furthermore, the negative cathode on a gaseous tube is subjected to the destructive effect of the bombardment of the positive ions.

Focusing in such tubes also depends upon the 'slow ions being more or less in equilibrium and the frequency of deflection can easily become so high that the focusing condition does not have time to re-establish itself after one deflecting impulse before the next deflecting impulse takes place, and some gaseous tubes will not focus satisfactorily at high frequencies.

Another disadvantage is that'as the deflecting voltage passes through zero in a gaseous tube, a barely perceptible mark appears in the line on the screen, due to ions in the path between the deflecting plates, although this seldom causes any trouble except in the most exacting work.

One ofthe objects of the invention is the provision of a focusing means for cathode rays which operates independently of any residual gas and which may, therefore, be incorporated in tubes in which the residual gas is reduced to a minimum.

Another object is the elimination of the destructive effect of the positive ions on the negative cathode of cathode ray tubes by providing an improved method of focusing which does not re quire the presence of residual gas.

Another object of the invention is the provision of an improved method and/or apparatus for focusing cathode rays which operates upon principles analogous to those of lenses used for light rays, and by means of which focusing can be controlled more accurately.

Another object of the invention is the provision of an improved method and/or apparatus for focusing cathode rays which are not afiected by temperature, progressive clean-up, pollution by occluded gases or by other gaseous conditions in the tube.

Another object of the invention is the provision of a new system of electrostatic focusing of cathode rays, which is peculiarly adapted to high vacuum or hard tubes, and which is capable of sharper focusing than the devices of the prior art.

Other objects and advantages of the invention will be apparent from the following description and the accompanying drawings, in which similar characters of reference indicate similar parts throughout the several views. i

- Referring to the three sheets of drawings,

Fig. 1 is a fragmentary sectional view, showing a cathode ray tube with the envelope in section,

and the elements of the tube in elevation, a part of the tube being broken away to indicate that the tube is of greater length than the part shown;

Fig. 2 is a similar fragmentary view of the lower I elements of the tube of Fig. l, with the elements shown in section, taken on the plane of a line determined by the axis of the tube;

Fig. 3 is an enlarged view of the filament and grid elements, the cathode and grid being shown in section;

Fig. 4 is an elevational view of the elements of a modified form of tube;

Fig. 5 is an elevational view of the same elements, with parts of the tube in section, taken on the plane of the line 5-5 of Fig. 4;

Fig. 6- is a top plan view of the structure of Fig. 4;

Fig. 7 is an enlarged sectional view of the filament and grid of the tube of Fig. 4;

' Fig. 8 is an elevational view of the elements of a modified form of tube, shown in full size;

Fig. 9 is a fragmentary sectional view of the tube of Fig. 8, taken on the plane of the line 9-9 of Fig. 8, looking in the direction of the arrows;

Fig. 10 is a horizontal cross-sectional view taken on the plane of the line l0lll of Fig. 9, showing point of deflection, and the curvature is also advantageous from the point of view of withstanding the pressure on the exterior of the tube caused by the atmosphere. The interior surface of the glass face 23 is covered with a suitable fluorescent material, such as, for example, willem ite. The lower part of the tube is usually provided with an inwardly extending glass support 24, in which all of the leads are sealed, and which provides a support forthe various wires which support the elements.

The cathode ray tubes constructed according to the present invention may be provided with any of the conventional forms of filaments, cathodes and grids. The tubes are preferably evacuated to the highest vacuum which can be accomplished, and the vacuum is enhanced by the use of a getter, which is indicated by the numeral 25. The degree of vacuum will naturally depend upon the facilities available and the point to which it is economically advantageous to evacuate the tube, but the present devices effect a focusing of the rays without the use of any gas, and are, therefore, adapted tothe hardest type of tubes.

The inside wall of the glass envelope may be coated with a thin electrically conducting layer of suitable metal or form of carbon, a connection to which may be brought out by a vacuum tight sealed wire through the glass wall. This coating may extend from theregion opposite the first anodes 60 and ii to any distance along the wall up to the fluorescent coating on the curved end of the envelope. This coating may be connected to the same positive potential as the anode 39 or operated at higher or lowervoltages than this anode. This coating prevents the accumulation of electric charges on the glass wall. It may also. serve as a substitute, for the high voltage anode 39, in which case all other parts and electrodes are disposed in the same way as pictured, but focusing is accomplished between this conductive coating on the glass wall and principally the anode indicated as 60. The theory of operation inthis case is-identical to that-described for the cylindrical anode illustrated and described and 1abelled 99.

Referring to Fig. 3, the supporting leads 26, 21 carried by the glass 24 may be utilized both for the support of the filament 29 and as electric conductors. Leads 26, 21 may be provided with fixed collars 29, upon which rests the mica disc 30, through which the filament passes.

The collars 29 comprise small tubular metal members formed with a radially extending flange 3i at one end, and they may be secured to leads by soldering or by merely de-forming the tubular portion with pliers or other clamping means until it clamps the wire lead upon which it is placed.

The filament 29 is preferably a non-inductive coil which is formed by bending a conductor of suitable length back upon itself and coiling it helically upon a mandrel so that for each coil having current passing in one direction there is a corresponding adjacent coil having current returning in the opposite direction to neutralize the inductive effect of these coils. The respective turns of the coils'are, of course, spaced from each other, and by means of an elongated coil of this type a more sturdy filament may be made than one of shorter length; which would necessarily have to be thinner and more fragile inorder to secure sufllcient resistance for the voltages which are to be applied to the filament.

The cathode may consist of a nickel tube 22, one

flat end of which rests upon the mica disc 39. the tube being arranged in spaced relation to the filament, but close enough thereto to be heated. and it is supported by a nickel wire lead 99, which passes through the mica plate and aids in holding the cathode in definite position with respect to thefilament and other parts.

The filament is preferably made of tungsten wire, and the cathode preferably made of nickel, which is coated with barium or strontium carbonate, in order to secure emission of electrons from the cathode.

The grid 34 may consist of a cup-shaped nickel member having a cylindrical portion 95 and a fiat end portion 39, which is provided with a centrally located aperture 91. The aperture 91 restricts somewhat the flow of the electrons from the cathode, and may be of the usual size employed in tubes of the prior art.

The grid may also consist simply of a metallic cylinder without the apertured capped end, this cylinder to be coaxial with the cathode in the same manner as described and illustrated for the conventional grid.

The grid is carried also by, the mica disc 20, and is held in place by being welded to a nickel lead wire '39, which also preferably passes through the mica disc.

The tube is preferably provided with an accelerating cylindrical anode 39, and with the pairs of deflector plates 40, 4|, 42 and 43, arranged so that the beam will pass between the plates of each pair, and the plates of each pair being arranged at right angles to the plates of the other pair.

The accelerating anode 39 may comprise a tubular member of nickel, which is supported by means of the mica discs 44, 45. The anode 99 has welded to it or otherwise fixedly secured thereon a pair of wire rings 46, 41, which serve as shoulders for engaging one side of each of the mica plates. The leads 49, 49, which comprise relatively stiff nickel wires,-and are used as the leads for the deflector plates 4| and 49 respectively, are fixedly secured in the glass supporting portion 24, and pass upward parallel to each other, but spaced from the other elements of the tube, and pass through the mica discs 44, 45.

Mica discs 44, 45 may be secured to these leads and others by additional ferrules 29 of the same type described with respect to the filament, the ferrules being clamped on the wires on each side of the mica discs 44, 45, so as to clamp the discs between the fianges of the ferrules.

The ferrules are so arranged upon these leads that the mica discs engage the wire shoulders 49, 41 and thereby confine them between the mica discs and secure the accelerating anode 39 to the mica discs, which, of course, have apertures for passing the anode. Additional leads 50 and SI also extend through the mica discs 44, 49, to which they are secured in the same manner by ferrules 29, and carry at their upper ends the deflector plates 42, 43. At their lower ends the leads 50, 5| also are connected to suitable wires,-

amazes ing substantially to the diameter of the accelerating anode 39 to save material, and the plates 40, M may be made slightly wider, in order to more certainly cover the range of movement of the deflector beam.

All of the deflector plates are secured together in the same manner, and therefore the securing means will be described with respect to only one pair of plates. For example, plate 0| is provided with a pair of laterally projecting wires 58, 51, which are welded to the upper portion and outside of the plate. The outer ends of these wires are secured in the glass insulators 58, 59, which comprise substantially cylindrical portions of glass, in which the wires are embedded.

The plate 60 is likewise provided with wires which are embedded in the insulators 50, 59, and plates #0, ii are thus secured in spaced relation to each other at their upper edges. The leads 68, it serve to secure the plates at their middle or lower portions, and the plates are thus held substantially parallel to each other.

It has already been pointed out that plates 42, iii are arranged at right angles to plates 30, M, the plates 82, 33 being also supported by their leads and by suitable wires and glass insulators in spaced relation and parallel to each other.

The cathode ray tubes are also preferably provided with focusing anodes, which may comprise the apertured discs 60, iii. In some embodiments of the invention, one of the apertured focusing discs Bi, which is nearest to the filament, may be omitted, as I have constructed tubes without it which work satisfactorily, but considerable difilculty is experienced in the alignmentof the elements of these tubes, and the first or lower disc facilitates the manufacture by making it easier to make a commercial tube that will work. Furthermore, there is less less of electrons by spreading when bothdiscs are employed, and therefore, I prefer to use the two focusing anodes. The second disc 60 is essential.

The first anode labeledlil may be used asa control element to vary the quantity of the electron stream focusing through it and hence varying the brilliancy of fluorescence. This may be accomplished by simply varying the normal potential applied to it. Alternating currents may be superimposed on the normal direct voltage connected to this anode, which will 'cause its density of the electron beam to vary in accordance with the magnitude and frequency of the impressed A. C. Bythis means the tube can be modulated for various purposes, such as television.

These anodes may consist of nickel d scs which are provided with circular apertures 62, 63, similar in size to the aperture in the grid. Holes as, large as 0.1 inch have been used, and the others, range from 0.025 to 0.25 inch. The sizes" of apertures mentioned herein are not to be regarded, however, as definite limits. The smaller apertures may assist in confining the beam to smaller limits in the course of its travel, but they also increase the difficulties of alignment of the 'elements of the tube, since all of the elements must be arranged substantially along the axis of the tube. The focusing anodes or discs B0', 6l must be arranged substantially parallel to each other and at a predetermined distance from each other or from the source of electrons.

I have termedthe focusing anodes 60, 8| discs,

--although, in fact, they are shown in Fig? 2 as being substantially cup-shaped, each focusing anode having a cylindrical portion .64, which is mounted upon a glass tube 85. The anodes 60 and lil arc, in fact, discs in so far as their electrical properties are concerned, since the glass tube 65 effectively shields all parts of them except the flat or disc surfacefrom the electron beam. The only action of these anodes on the beam is that of two discs. The cylindrical portion 04 is, however, insulated from the electron beam by the glass tube 65, andis merely included as a support for the focusing anode discs 60, 6 I. Each of these cylindrical portions is welded to laterally extending wires, which in turn are welded to the same leads 66, 61, so that when the focusing anodes are both at the same potential, only one of the leads 06, 61 need be brought out of the tube.

The arrangement of the focusing anode or anodes with respect tothe other elements is one of the most important features of the present tube, and I have discovered that there is a definite relation between the voltage which is applied to the accelerating anode or cylinder and the voltage applied to the focusing discs, which depends upon the distance between the upper focus ing disc 00 and the source of electrons. For example, when a potential of 2,000 volts is applied to the accelerating anode or cylinder 39, and a potential of 300 volts is applied to the focusing discs 60, 0!, the disc 00 is approximately one and one-quarter inch from the source ofv electrons, and with these voltages the beam is focused sharply upon the fluorescent screen of the face 23 by means of focusing discs.

The foregoing figures are not to be regarded as' mathematically accurate, as it is my custom to first construct the tube with its focusing-disc at a predetermined spacing to the other elements, and then experimentally determine the exact ratio of voltages or the voltages which are applied to the focusing disc and an accelerating anode, to effect the best focusing. I have discovered that when the spacing between the focusing anode and source of electrons is changed, the voltage applied to-the focusing anodes and accelerating anode should also be changed accordingly, and the relation between these parts and the potentials is analogous to the spacing of the lens of a light ray system. Thus, predetermined voltages'and spacing produce a focus on the screen at a certain distance, and if the tube is changed in size the factors of applied voltages and anode spacing must be changed accordingly, primarily the latter.

The focusing is independent of the presence of any residual gas, and therefore eliminates the disadvantages enumeratedabove, of the prior devices which employ residual gas for focusing, and tubes constructed according to the present invention have a'life which corresponds to the life of the best audion tubes. The usual potentials are applied to the grid, the filament, and the deflector plates, and the present tubes may be utilized in any manner in whichthe cathode tubes of the prior art may be utilized, for television, etc.

Referring to Figs. 4 to 'I, this is a modification Referring to Fig. 7, the filament 68 comprises a tungsten filament, bent in the form of a loop, and having a small nickel rod disc or wire 89 welded to the ends of the two wires forming the filament loop. The nickel disc 89 is coated with barium or strontium carbonate, in order to provide for the emission of electrons therefrom, and the source of the electrons and the filament are covered by the grid 34.

In this case the focusing discs 80 and ii are again vsupported upon a glass tube 85, which in mm is supp rted by means of a metal tube 10 embracing the glass tube. The metal tube I is welded to the rectangular wire brackets II at each side, which brackets have downwardly proecting wire ends 72 that are embedded in the :lass insulators I3 carried by wire supports ll.

Referring to Figs. 8 to 10, this is another modfication. in which many of the elements may be he same as described with respect to Figs. 1 to 3. ."he deflector plate leads 48, 49, 50 and SI are overed with the glass tubes extending from a pint adjacent the deflector plates to a point he- )W the top of the grid.

In order to support these last tubes in place, ach of the leads may be provided with a ferrule 5 clamped on the wire above the tube, and a fermle I6 clampedon the wire below the tube. The ibes and leads 50-48 are secured to the acalerating anode 39 by means of a pair of metal raps or bands 11, 18, which may comprise strips 3 sheet metal, such as nickel, having their ends elded together and shaped complementarily to re opposite outer outline of the insulating glass lbs: on leads -54, and the accelerating anle 8.

In other words, each band has four flat portions I, each of which may be welded or otherwise cured to the accelerating anode 39, and each and has four partially cylindrical portions 80, mich frictionally grip the glass tubes whichsurund the leads 5fl54. The lower ends of these ads may be connected to the usual wires that are aled in the glass supporting base 24. In this se the accelerating anode and the upper focusg disc are mounted spaced relation to each her by the angle shaped wires 8 l-Bl. One end wire BI is secured to the accelerating anode,

band 18 by welding, and the other end is emdded in insulator body 85 of glass, lava or other mlating material. The other wire 82 is secured a like manner to the glass insulator body 85 and the cylindrical flange of the focusing disc 80. it will thus be observed that I have invented a lrality of improved forms of cathode ray tubes which the focusing of the beam does not depend on the presence of residual gas, so that the tube Ly be evacuated as much as possible to eliminate undesirable effects of residual gas. The prest tube is, so far as I am aware, the first one in ich the distance between the focusing and :elerating anode combination and the grid bears lirect relation to the distance from the accel- .ting anode at which a focus will be obtained, or

which the spacing of the focusing disc from the tree of electrons bears any relation to the xentials applied and to the place at which a us of the electron beam takes place. By means my improved method and apparatus the cathrays may be focused more sharply and accuely, and the present tubes are admirably suited be used for exacting work in television, oscillorphs, etc.

While I have illustrated and described a preopposite end of said envelope,

ferred embodiment of my invention, many modifications may be made without departing from the spirit of the invention, and I do not wish to be limited to the precise details of construction set forth, but desire to avail myself of all changes 6 within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States, is:

1. A cathode ray tube adapted to have its cathl0 ode rays focused, comprising an envelope evacuated to such a high vacuum that there are substantially no visible ionization eflects, a source of electrons within said envelope and located at one end of said envelope, a translucent fluorescent screen carried by said envelope and located at an a focusing anode comprising an apertured electrical conducting diaphragm, located between said source and said screen, with its aperture in alignment with a beam 0 porting said anodes in said envelope and insulating said anodes from each other, the spacing of said focusing anode from said source depending upon the potential gradient adapted to be maintained between said anodes to cause the electron stream to be projected toward said screen and to produce a focus of the beam at a sharply defined point on said screen.

2. A cathode ray tube ode rays focused,

said diaphragm and tubular electrode being located close together but out of contact with each other and both being at a greater distance from said source of electrons than they are spaced from each other, said tube including means for supporting said anodes in said envelope and insulating said anodes from each other, the spacing of said focusing anode from said source depending upon the potential gradient adapted to be maintained between said anodes to cause the electron stream to be projected toward said screen and to produce afocus of the beam at a sharply defined point on said screen, and a modulating electrode comprising a tubular metal member having one of its ends covered with an apertured disc and located between said focusing diaphragm and the source of electrons.

3. A cathode ray tube adapted to have its cathode rays focused, comprising an envelope evacuated to such a high vacuum that there are substantially no visible ionization efiects, a source of electrons within said envelope and located at one end of said envelope, a translucent fluorescent screen carried by said envelope and located at an opposite end of said envelope, a focusing anode comprising an apertured electrical conducting diaphragm, located between said source and said screen, with its aperture in alignment with a beam of electrons from said source, said diaphragm being in a plane at substantially right angles to the direction of said beam, and an accelerating anode of the tubular type constructed of electrically conducting material and located between said focusing anode and said screen, said accelerating anode having a substantially larger diameter than the aperture in said diaphragm and having its axis in substantial alignment with said source and the aperture in said focusing anode, said diaphragm and tubular electrode being located close together but out of contact with each other and both being at a greater distance from said source of electrons than they are spaced from each other, said tube including means for supporting said anodes in said envelope and insulating said anodes from each other, the spacing of said focusing anode from said source depending upon the potential gradient adapted to be maintained between said anodes to cause the electron stream to be projected toward said screen and to produce a focus of the beam at a sharply defined point on said screen, said accelerating electrode comprising a metal cylinder, and said tube having a layer of conducting material carried by its inner surface from a point adjacent said screen to a point adjacent the source of electrons, said conducting layer being adapted to be charged with a positive potential.

4. In a focusing arrangement for cathode ray tubes, the combination of a supporting base with a plurality of leads carried by said base, certain of said leads being connected to and supporting a source of electrons, certain other of said leads extending beyond said source of electrons and supporting a pair of oppositely disposed metal caps, said caps being mounted upon an insulating sleeve to maintain said caps in alignment, and said caps being provided with aligned apertures, another lead carried by said base and connected to and assisting in the support oi an accelerating cylinder, said accelerating cylinder being insulated from said caps and being located in substantial alignment with said caps, the farthermost of said caps being spaced from the source of electrons a predetermined distance, depending upon the voltage adapted to be applied to said accelerating electrode and said caps, to effect a focusing of the cathode rays. and oppositely disposed insulating connections betw said accelerating electrode and the adja metal cap for maintaining the alignment of i electrode and cap, a pair of metal bands car: by said accelerating electrode and embracin plurality of insulating tubes, other leads in insulating tubes, and supporting a pair of e trostatic deflecting plates in substantial ali ment with said accelerating electrode.

5. In a focusing arrangement for cathode tubes, the combination of a supporting base v a plurality of leads carried by said base, ceri of said leads being connected to and suppori a source of electrons, certain other of said 16 extending beyond said source of electrons supporting a pair of oppositely disposed in caps, said caps being mounted upon an insulai sleeve to maintain said caps in alignment, 1 said caps being provided with aligned apertu another lead carried by said base and conne( to and assisting in the support of an accelerai cylinder, said accelerating cylinder being it lated from said caps and being located in s stantial alignment with said caps, the fartl most of said caps being spaced from the $01 of electrons a predetermined distance, depenc upon the voltage adapted to be applied to said celerating anode and said caps, to effect a for ing of the cathode rays, a pair .of metal be carried by said accelerating electrode and 1 bracing a plurality of insulating tubes, 01 leads in said insulating tubes, and supportin pair of electrostatic deflecting plates in subst tial alignment with said accelerating electr' and auxiliary insulating connections between: electrostatic deflecting plates for holding plates in predetermined spacing and relation: to each other.

6. In a focusing arrangement for cathode tubes, the combination of a support with a; 1 rality of leads supported thereby, a source electrons carried by certain of said leads an modulating electrode comprising a cylindr member having its outer end capped with apertured diaphragm, said aperture being alignment with the source for emission of e trons, a pair of cylindrical cap-shaped an: oppositely disposed and mounted on an insulai tubular member carried by other predetermi leads, said latter caps being provided with a tures in alignment with the source of electn and a tubular accelerating electrode located alignment with said tubular insulating mem and carried by other predetermined leads, i latter predetermined leads passing through a 1 of insulating discs secured to said leads, and: discs being engaged on the opposite sides of shr ders carried by said accelerating electrode, 4 tain of said latter predetermined leads exte ing beyond said accelerating electrode and s porting pairs of oppositely disposed electrost deflecting plates, said pairs being arranged tra versely to each other in a substantial alignm with said accelerating electrode and source electrons.

JESSE E. BROWI 

